1. Field of the Invention
The present invention relates to method and system for paging for a Mobile Station (MS) in a General Packet Radio Service (GPRS) wherein the Base Stations (BSs) comprise a portion of the routing area-cell mapping information.
2. Description of the Related Art
Wireless communications have changed over the last decade, evolving from the first generation of analog cellular service, to the second generation of digital cellular service. Among other advantages, digital cellular service allows subscribers to receive enhanced voice and data communications, while increasing the number of channels available in a given area. However, as the demand for wideband wireless data transmission becomes more and more significant, and since cellular operators foresee a great business opportunity in fulfilling the subscribers' request for the wireless wide-band transmissions, a third generation of cellular networks is under way of being achieved and implemented. The third generation of cellular networks allows wide-band voice and data transmission at rates of up to 2 Mega-bits per second, and make use of improved existing technology. For example, the Wide-band Code Division Multiple Access (W-CDMA), the Enhanced Data rates for Global Evolution (EDGE), and the General Packet Radio Service (GPRS) are all third-generation technologies that may provide high-speed connection of a Mobile Station (MS) in a pure third-generation cellular network, or in a network comprising both third-generation systems combined with legacy systems (second generation and first generation systems).
In particular, GPRS is a packet-based wireless communication service that can provide transmission data rates from 56 up to 114 Kbps and continuous connection to the Internet for MSs and computer users. The higher data rates will allow users to take part in video conferences and interact with multimedia Web sites and similar applications using mobile handheld devices as well as notebook computers. GPRS is based on Global System for Mobile (GSM) communications and will complement existing services provided by the legacy systems. In theory, GPRS packet-based service should cost users less than circuit-switched services since communication channels are being used on a shared-use, as-packets-are-needed basis rather than dedicated only to one user at a time. It should also be easier to make applications available to mobile users because the faster data rate means that middleware currently needed to adapt applications to the slower speed of wireless systems will no longer be needed. Once GPRS becomes available, mobile users of a virtual private network (VPN) will be able to access the private network continuously rather than through a dial-up connection.
A typical GPRS network comprises a Gateway GPRS Support Node (GGSN) which acts as an interface between the packet core network and the public IP network, a Serving GPRS Support Node (SGSN) which is the GPRS network's switching node, a GPRS Home Location register (HLR) holding the subscribers' data, a plurality of Base Station Controllers (BSCs), each managing one or more Radio Base Stations (RBSs) which are responsible for the actual radio communications with the MSs. Cellular operators' requirement for flexible open systems is driving the implementation of Internet Protocol (IP) based networks. Such an IP connection may be implemented between the SGSN and the BSCs and further between the BSCs and the RBSs.
Current GPRS systems combined with and deployed in GSM networks make use of the BSCs to initiate paging on the Packet Data Control Channel (PDCH), which is the channel type used in GPRS between the BSCs and the RBSs. Communications between the SGSNs and the Radio Access Network (RAN) are governed in a GPRS network by the Base Station Subsystem GPRS Protocol (BSSGP), herein enclosed by reference. A Packet Control Unit (PCU) located in each BSC is responsible for interpreting the BSSGP page messages received from the SGSN, and for passing the page requests to the BSC application software, which in turn initiates the actual page on the PDCHs associated with the routing area (RA) designated in the BSSGP page message received from the SGSN.
However, in the situation described hereinbefore, wherein a page for a particular MS is initiated by the network, it has been noticed that the time required for a page to be transmitted on the air interface may be significantly increased in a 3rd generation IP-based radio access network. This is due to the non-dedicated nature of the IP-based transmission that require longer time for packet data signaling than in the legacy systems wherein control channels were allocated a particular physical communication link.
In particular, in a GPRS network, the Radio Network Server (RNS) typically communicates directly with the SGSN and handles all real-time activities of the RAN, which may comprise the set of BSCs and RBSs. Such real-time activities comprise the page processing using routing area-cell mapping information, i.e. the real-time interpretation and conversion of each page destination address into cell page signals to be transmitted to the controlling RBS from the RNS, seizure of traffic channels and updating of radio parameters in the RBS. The Radio Network Management Control Point (RMCP) is the GPRS network node dedicated to the non-real-time activities related to the RAN, such as the storing of the routing area-cell mapping information and cells configuration in an information database, which regularly updates RNS with parameters related to real-time page processing. However, it has been noticed that in the IP-based GPRS RAN configuration wherein the SGSN acquires knowledge of the RA from the network management system, the time for the page to reach the intended MS is increased when compared with second generation (2G) radio access networks. This is because the page sent from the SGSN and containing RA information must pass via the RNS, which is located in the radio access network, then sent on a non-dedicated channel toward the RBSs for finally being radio broadcast.
In order to support higher data rates and real-time applications the European Telecommunications Standards Institute (ETSI) GPRS are currently being modified to cover the introduction of EDGE-based GPRS technology for the GSM and ANSI-41 markets. For supporting such higher data rates, GPRS designers may propose to include the Radio Link Control/Medium Access Control (RLC/MAC) functionality of the PCU in closer physical proximity to the Channel Codec Unit (CCU). This is believed to eliminate delays which would be introduced when communications between these two physical/functional entities are performed over an IP-based RAN. Voice-over-IP implementation is particularly sensitive to this delay. However, such a change will have impacts on currently used scheme for handling the routing area-cell mapping processing for each page, and there is currently no solution for this matter.
It would be advantageous to have a more straightforward way for sending a page request from the SGSN to the RBSs than in the scenario described hereinbefore. It would be even more advantageous to have a page request being send without the need to pass through a BSC, wherein the routing area-cell-mapping processing would be delegated to each RBS receiving the page, so that the intermediate processing of the page request is avoided.
The present invention describes such a solution.